1. Field of the Invention
The present invention relates to an X-ray tube and an X-ray analysis apparatus to be used for, for example, an energy-dispersive X-ray fluorescence analysis apparatus, which are suitable for small and lightweight handy X-ray analysis and portable X-ray analysis apparatuses.
2. Description of the Related Art
X-ray fluorescence analysis is used for qualitative analysis or quantitative analysis of a sample in the following manner. A primary X-ray emitted from an X-ray source is radiated to the sample. Then, a fluorescent X-ray emitted from the sample is detected by an X-ray detector to obtain a spectrum from energy of the fluorescent X-ray. The obtained spectrum is then subjected to the qualitative analysis or quantitative analysis. Since the X-ray fluorescence analysis enables the quick and non-destructive analysis of the sample, the X-ray fluorescence analysis is widely used in process and quality control or the like.
As analysis methods in the X-ray fluorescence analysis, there are a wavelength-dispersive method for splitting a fluorescent X-ray by an analyzing crystal to measure a wavelength and an intensity of the X-ray, an energy-dispersive method for detecting a fluorescent X-ray with a semiconductor detector without splitting the fluorescent X-ray to measure an energy and an intensity of the X-ray with a pulse height analyzer, and the like.
Conventionally, for example, in Japanese Patent Application Laid-Open No. 8-115694 (hereinafter, referred to as Patent Document 1), in order to increase sensitivity to the fluorescent X-ray, the following attempt has been made. An X-ray tube is provided with an extraction window for externally obtaining a fluorescent X-ray which has passed through the X-ray tube. In this manner, the X-ray tube and an X-ray detector are brought closer to a sample.
In addition, as described in Japanese Patent No. 3062685 (hereinafter, referred to as Patent Document 2), with the reduction of the X-ray tube and the X-ray analyzer in size, a handy energy-dispersive X-ray fluorescence analysis apparatus is diffused.
The above-mentioned conventional techniques still have the following problems.
For example, the X-ray analysis apparatus described in Patent Document 1 has a great effect in increasing the detection sensitivity by bringing the X-ray tube and the X-ray detector closer to the sample. However, since each of the X-ray tube and the X-ray detector has a size that is limited but equal to or larger than a certain size, a degree of the approach of the X-ray tube and the X-ray detector to the sample is also limited.
On the other hand, the conventional handy energy-dispersive X-ray fluorescence analysis apparatus is requested to be further reduced in size as well as in weight. However, since the X-ray tube and the X-ray detector occupy most of the X-ray analysis apparatus in view of volume and mass as an apparatus configuration, the conventional apparatus configuration has a limit in reduction in size and weight. Further, since the handy energy-dispersive X-ray fluorescence analysis apparatus is an open-type apparatus which directly radiates a primary X-ray to a sample in an atmosphere instead of housing and analyzing the sample in a hermetically sealed sample chamber, the amount of X-rays generated from the X-ray tube is restricted for X-ray safety reasons. Therefore, it is necessary to more efficiently detect the fluorescent X-ray from the sample.